Thinly slice the top sirloin steak against the grain into bite-sized strips.
Season the steak strips evenly with the sea salt, black pepper, and garlic powder.
Heat the olive oil in a large non-stick skillet over medium-high heat.
Add the steak to the skillet and sear for 2-3 minutes until browned and cooked through, then transfer to a plate.
In the same skillet, add the sliced bell peppers and red onions, sautéing for 4-5 minutes until they are tender and slightly charred.
Wipe the skillet clean and return it to medium heat, then place the tortilla in the pan.
Sprinkle half of the shredded cheddar on one side of the tortilla, then layer on the cooked steak and sautéed vegetables.
Top with the remaining cheese and cilantro, then fold the tortilla in half to close.
Cook for 2 minutes per side until the tortilla is golden brown and the cheese has completely melted.
Remove from the pan and let rest for one minute before slicing into three wedges.